Below is a stepwise walk through of how a snowblower works. It
starts at the engine and describes how power is transferred by naming the
components that get the power.
The motor
Motors have a horizontal crankshaft that turns at 3200 to 3600 RPM.
Part of the motor crankshaft sticks out of the motor and has a pulley
attached to it which supplies power to the rest of the snowblower. The
pulley is to the middle right side. It gets the belts. This snowblower has
two belts on one pulley
Engine Pulley
The engine crankshaft
pulley drives one or two thin belts depending on the design. This
motor drives one pulley the dark one of the three. The top pulley
drives the large pulley at a great reduction to transfer power. The
smaller light brown pulley is the tensioner pulley. When you pull
down the handlebar lever it moves the tensioner pulley into the belt
tightening it to drive the lower large pulley. The
description below is of a two belt system but a one belt has similar
components.
Belts
The belts run down into the tractor section
(where the wheels are) to
drive two big pulleys. The bigger pulleys slow down the speed of the
motor because they have a much larger diameter than the engine
pulley. They also have more power or torque because of the diameter
difference.
Tractor drive pulley
One belt drives the tractor pulley. This pulley transfers power to a
rotating shaft.with a metal disk or plate on it. The large pullet at
the bottom. The view is into the tractor base.
Metal friction disk drive Plate
The metal plate is in the middle and just a rotating surface which has a lot of drive power
from the big pulley. It's just a spinning disk 4 to 8 inches in
diameter.
Friction disk
Another disk inside the tractor section has a rubber like hoop attached to
its diameter. It's alignment to the metal friction disk drive plate is 90 degrees.
When clutch on the handlebars is pressed the drive plate is brought up to touch the
friction disk which turns with great force.
Clutch
One lever on the handlebars is for the moving the drive plate up to the friction disk. It's the snowblower drive clutch.
Axle and gears
The turning friction disk rides on a shaft, usually with 6 sides called a
hex shaft. The shape is for good grip. If it was round the
friction disk might slip on the axle. The axle turns with the frin
ction
disk and drives a gear attached to the hex shaft. It's small to reduce the motor speed
again and get more power.
Chains and gearing
The small gear generally drives a chain attached to another axle which the
wheels ride on. Manufacturers have various gearing arrangements for
driving the wheels but basically a chain drives another gear on another
shaft who's ends stick out of the tractor body and have wheels attached.
Auger pulley
A second belt and pulley are driven by the pulley on the motor crankshaft is the auger
pulley. It is inside the tractor body close to the tractor drive
pulley.
Impeller shaft
The auger pulley drives a shaft which goes runs from the tractor body into the
intake housing. The impeller, auger gearcase and auger blades are
driven off this shaft.
Impeller
The shaft goes from the tractor
section into the intake housing. An impeller is attached to the shaft and is
located at the back of the intake housing. It gets spun at about 1200
RPM. The impeller tosses out the snow collected by the augers.
Auger gear case
The auger gear case is a box that holds a worm gear and a helical
gear. The impeller shaft runs into the auger gearcase to drive it
via a worm attached to it's end.
Worm gear
The worm is spiral shaped so it can turn the helical gear which is at
right angles to the worm. The worm rides on the same shaft as the
impeller so is driven by it.
Helical gear
The auger case that holds the worm and helical gear has the worm on top and
the helical gear below. The helical gear has its gear teeth on the
outside. The inside is hollow so like a doughnut with teeth on the
outside and a hold in the center. A shaft goes through the hole - the auger
blade axle.
Auger blade axle
The auger blade axle is pinned to the helical gear so turns with it.
The axle is supported by bearings attached to the sides of the intake
housing. The left and right auger blades are mounted on the auger
blade axle.
Auger blades
The auger blades are attached to the auger blade axle by a pin of some
sort. The pins can be shear pins, shear bolts or breakable cotter
pins. The blades turn with the helical gear and auger blade axle under
tremendous force. If some object is hit the shear bolts will break at
a low enough force that the pressure is relieved in the auger gear case and
prevent damage inside the case or back up the line through the gears, belts
and pulley to the motor.
Auger gear case
The auger gear case gives support to the worm, helical gear and auger blade
axle. Inside the case are bearings which support the impeller shaft
that has the worm on it's end. The worm turns inside the case
supported by two bearings. The auger blade axle also runs through the
auger gear case and supported by bearings.
Auger clutch
The auger blades are engaged from the handlebars by a lever. The lever
generally causes a tensioner pulley to move into the auger drive belt to
tighten it. That causes the drive pulley on the crankshaft to drive
the auger drive pulley.
Grease
The auger gear case is filled with grease to lubricate the worm, helical
gear teeth, and lubricate the auger blade axle. Grease with an EP
(extra pressure) rating is used.
Driving around
You start the motor and engage the drive lever. The snowblower starts to
move. When you approach snow you hold down the auger lever and it
engages the blades. The blades collect the snow into the back of the intake
housing. The impeller then tosses it out of the chute.
Speeds
The metal rotating disk above is about 8 inches in diameter. The
friction disk gets pulled up to touch this disk to move the wheels. If
the friction disk is near the center if the drive plate the wheels go
slow. If the friction disk is moved with the drive selector the
friction disk can be moved to the outside of the drive plate which caused
the friction disk to turn faster. Makers provide speed settings
somewhere up at the handlebars which causes the friction disk to move across
the drive plate giving various speeds. Most new or old snowblowers
have about the same size drive plate. The new snowblower just have
more selections of speeds but generally no faster or slower than the old
snowblowers. For example an old snowblower may have 3 to 5
speeds. Newer snowblowers usually have 5 to 6 speeds. The high
and low speeds of new and old snowblowers is about the same with the newer
snowblowers having a slight advantage on the very fast speeds.
Reverse
You get to the end of the drive way and disengage the drive clutch.
How does reverse happen. The shift lever moves the friction disk to
the other side of the drive plate. The plate turns the friction disk
one way at 3 o'clock and the opposite way at 9 o'clock. Reverse is
that simple.
